Consider a proper socket callback for starting sockets

Author: LostKobrakai

lib/phoenix/endpoint.ex

@@ -360,6 +360,13 @@ defmodule Phoenix.Endpoint do
 
   # Channels
 
+  @doc """
+  Provide module specs for sockets to start and drain with the endpoint.
+
+  See `Phoenix.Socket.Transport` for more information.
+  """
+  @callback sockets() :: [{module(), keyword()} | module()]
+
   @doc """
   Subscribes the caller to the given topic.
 
@@ -406,15 +413,13 @@ defmodule Phoenix.Endpoint do
   """
   @callback local_broadcast_from(from :: pid, topic, event, msg) :: :ok
 
+  @optional_callbacks sockets: 0
+
   @doc false
   defmacro __using__(opts) do
     quote do
       @behaviour Phoenix.Endpoint
 
-      def __start_sockets__ do
-        unquote(Keyword.get(opts, :start_sockets, []))
-      end
-
       unquote(config(opts))
       unquote(pubsub())
       unquote(plug())

lib/phoenix/endpoint/supervisor.ex

@@ -119,7 +119,14 @@ defmodule Phoenix.Endpoint.Supervisor do
   end
 
   defp socket_children(endpoint, fun) do
-    for {socket, opts} <- endpoint.__start_sockets__(),
+    sockets =
+      if function_exported?(endpoint, :sockets, 0) do
+        endpoint.sockets()
+      else
+        []
+      end
+
+    for {socket, opts} <- Enum.map(sockets, &normalize_module_spec/1),
         # TODO is this the correct place for this?
         # Needs to know transport specific config
         # _ = check_origin_or_csrf_checked!(conf, opts),
@@ -129,6 +136,9 @@ defmodule Phoenix.Endpoint.Supervisor do
     end
   end
 
+  defp normalize_module_spec(module) when is_atom(module), do: {module, []}
+  defp normalize_module_spec({module, kw}) when is_atom(module) and is_list(kw), do: {module, kw}
+
   defp apply_or_ignore(socket, fun, args) do
     # If the module is not loaded, we want to invoke and crash
     if not Code.ensure_loaded?(socket) or function_exported?(socket, fun, length(args)) do

test/phoenix/integration/websocket_channels_test.exs

@@ -214,11 +214,14 @@ defmodule Phoenix.Integration.WebSocketChannelsTest do
 
   defmodule Endpoint do
     use Phoenix.Endpoint,
-      otp_app: :phoenix,
-      start_sockets: [
+      otp_app: :phoenix
+
+    def sockets do
+      [
         {UserSocket, []},
         {UserSocketConnectInfo, []}
       ]
+    end
 
     plug Plug.Session,
       store: :cookie,

test/phoenix/integration/websocket_socket_test.exs

@@ -115,11 +115,14 @@ defmodule Phoenix.Integration.WebSocketTest do
 
   defmodule Endpoint do
     use Phoenix.Endpoint,
-      otp_app: :phoenix,
-      start_sockets: [
+      otp_app: :phoenix
+
+    def sockets do
+      [
         {UserSocket, custom: :value},
         {PingSocket, []}
       ]
+    end
 
     plug Router
   end